The present invention relates to a coupling device for connecting a drive chain to a mineral mining machine, particularly but not solely to a plough.
As is well known in longwall mineral, e.g. coal, face workings, a machine such as a plough or shearer is driven back and forth along a guide at the mineral face side of a conveyor to win mineral. A chain is circulated within guide passages or channels inside the guide and the chain is connected to the machine inside one of these guide channels with simple fixed shackles or the like. It is, however, preferable to connect the chain to the machine with the aid of a coupling device permitting a certain amount of free swivelling motion. A coupling device of this kind is described in German Patent specification No. 2438651. This known coupling device has a casing in which a shackle or drawbar is rotatably supported. The drawbar is then fitted to the machine via a hook while the casing is fitted to the chain. Two such coupling devices would be used to connect the machine to the ends of the drive chain and the swivelling drawbars permit the chain to untwist itself thereby ensuring the chain runs onto the associated drive means in the correct position without its links becoming misaligned. The coupling devices run along the guide channel during use. Loose debris, especially fine coal dust, is apt to find its way into the guide passage and can cause jamming or blockage especially since the coupling devices themselves are of greater size than the chain links and simple shackles and tend to push the dust against the wall of the chain guide passages. After repeated runs, the material tends to compact and accumulate and adheres to the wall of the guide passage thus aggravating the problem.
A general object of the present invention is to provide an improved form of coupling device.